When transmitting a high data rate signal over an interface from a first chip or circuit with a first DC (direct current) bias or common mode voltage, to a second chip or circuit with a second DC bias or common mode voltage, DC blocking capacitors, also referred to as AC coupling capacitors, are used to isolate the DC behaviour on either side of the interface. Most high speed (e.g. 5 GHz plus) circuits are AC coupled, with board level capacitors. DC blocking capacitors between parts use board area, and degrade signal quality.
An example of a conventional off-chip AC coupling scheme is shown in FIG. 1. Shown is a first circuit 10 connected to a second circuit 14 through board level AC coupling circuit 12 including board level capacitors 16. Also shown is an interconnect 18 that typically has a voltage drop as a function of frequency. In conventional systems, this can be compensated for using an equalizer; however, active equalizers consume a significant power.